1. Field of the Invention
The present invention relates to a polishing solution distribution apparatus to distribute polishing solution for polishing a workpiece such as a silicon wafer for a semiconductor and a polishing apparatus having the same.
2. Description of the Related Art
In general, a silicon wafer for a semiconductor is to be shipped as a product through respective processes of lapping, etching, polishing, cleaning and inspecting after being cut out from an ingot by utilizing a diamond saw, a wire saw and the like. In the polishing process, a carrier which holds a workpiece being a polishing object is placed between a circular upper platen and a circular lower platen. Then, spinning and revolving of the carrier are performed while the upper and lower platens or only the lower platen is rotated as pouring polishing solution into an area sandwiched by the upper platen and the lower platen via a polishing solution supply hole arranged at the upper platen. Accordingly, upper and lower faces of the workpiece are polished.
In such a polishing process, it is important to improve processing accuracy of a workpiece as eliminating deviation of wear of a platen face by evenly distributing polishing solution to an area sandwiched by an upper platen and a lower platen.
Examples of a method to distribute polishing solution in the related art include a separate valve type having plural branch piping to adjust flow quantity of respective branch piping with separate valves, a pump supply type to adjust flow quantity with a proportioning pump, and a dropping type to distribute polishing solution dropping to a distributor with plural branch piping. With the separate valve type, it is difficult to adjust the flow quantity of each branch piping with adjustment of the separate valve and the adjustment operation is troublesome since the valves are arranged at a high location. With the pump supplying type, cost is increased since the pump is expensive. Accordingly, in general, the dropping type is adopted as disclosed in Japanese Patent Application Laid-Open No. 2005-186170, Japanese Utility Model Application Laid-Open No. 58-191957, Japanese Utility Model Application Laid-Open No. 47-43116, and the like.
Japanese Patent Application Laid-Open No. 2005-186170 discloses that distribution deviation of polishing solution is lessened by placing a sphere body at a funnel-shaped solution receiving portion to which polishing solution drops and adjusting flow quantity of the polishing solution with buoyancy force of the sphere body. Japanese Utility Model Application Laid-Open No. 58-191957 discloses a polishing apparatus in which upper and lower platens perform rotational motions to supply powder to a polishing face of the platen through plural tubes from a powder ring with a concave groove. Japanese Utility Model Application Laid-Open No. 47-43116 discloses a polishing apparatus in which equal quantity of polishing solution flows to each discharge port arranged at a distributor as filling sponge body into the distributor so that polishing solution dropping to the sponge body soaks throughout the sponge body.
With the above dropping type in the related art, there has been a problem that polishing solution cannot be evenly distributed when leveling for distributor installation is insufficient or inclination of an installation location varies after installation. Further, in Japanese Patent Application Laid-Open No. 2005-186170, there has been a problem that particles contained in polishing solution are solidified as a result of stagnant flow of polishing solution depending on weight of the sphere body. In Japanese Utility-model 47-43116, there also has been a problem that particles contained in polishing solution stagnate and are hardened at the sponge body.